Re: [PATCH 9/9] KVM: Adds support for halting in the kernel

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Gregory Haskins wrote:
> Halting in userspace requires a relatively cumbersome mechanism to signal the
> halted VCPU.  Implementing halt in kernel should be relatively straight
> forward and it eliminates the need for the signaling
>
>   

Merging this one in, found some nits:

> +/*
>   * This function is invoked whenever we want to interrupt a vcpu that is
>   * currently executing in guest-mode.  It currently is a no-op because
>   * the simple delivery of the IPI to execute this function accomplishes our
> @@ -2481,6 +2556,16 @@ static void kvm_vcpu_intr(struct kvm_irqsink *this,
>  			BUG_ON(direct_ipi == smp_processor_id());
>  			++vcpu->stat.guest_preempt;
>  		}
> +
> +		/*
> +		 * If the CPU is halted it will be waiting for a wake-up
> +		 */
> +		if (waitqueue_active(&vcpu->irq.wq)) {
>   

Why do the check?  The only reason I can see is to keep the stats 
correct.  Otherwise we can do the body of the if unconditionally.

> +			wake_up_interruptible_sync(&vcpu->irq.wq);
> +			set_tsk_need_resched(current);
>   

This is unneeded?  I'd expect wake_up_interruptible_sync() to take care 
of any rescheduling needed.

> +			++vcpu->stat.halt_wakeup;
> +		}
> +
>   


-- 
error compiling committee.c: too many arguments to function


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